08.26.13 5:35 PM ET

Tesla’s stock, having tripled in the past six months, has surged through $170. That valuation of its stock gives it a market capitalization of over $20 billion.

That’s stunning on many levels. By any measure, Tesla is a very small presence in the U.S. car market.

According to Autodata Corp, Tesla sold 1,470 cars in July of 2013. In the same month, General Motors sold 234,071, Ford 193,080, Chrysler 140,120 and Honda 141,439. In other words, the big established U.S. car companies sell well over a hundred times more cars than Tesla does every month.

And yet. The market capitalization for Ford is $66.4 billion. General Motors is $52.3 billion; Honda’s is $68 billion. And investors says Fiat, which owns Chrysler, is only worth is $7.3 billion.

In their wisdom, stock market investors have turned that Tesla is worth $13.6 million for every car it sold last month.

There is a rational basis for a part of the Tesla euphoria. The company is making products and selling them. With each passing week, more Teslas hit the road, and their owners start evangelizing. In the first quarter of 2013, just as the euphoria was kicking in, Tesla outsold similar-priced sedans from Mercedes-Benz, BMW and Audi. And, in the luxury car trend-setting market of California Tesla has cut itself 12 percent of the pie. The company also reported a surprise profit in the most recent quarter.

And yet the love affair does seem a bit overblown at this early juncture. Perhaps the big test for Tesla in terms of Wall Street’s affections will be when it attempts to scale up beyond the wealthy, niche markets in which it does well.